1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more particularly to a static electricity prevention type liquid crystal display panel that is adaptive for preventing static electricity from flowing through a pad part.
2. Discussion of the Related Art
A general liquid crystal display device displays pictures by controlling light transmittance of liquid crystal using an electric field. To this end, the liquid crystal display device includes a liquid crystal display panel, where liquid crystal cells are arranged in a matrix, and a drive circuit for driving the liquid crystal display panel.
The liquid crystal display panel includes a thin film transistor array substrate and a color filter array substrate, which are opposite to and spaced apart from each other and bonded together, spacers sustaining a designated cell gap between the two substrates, and a liquid crystal injected into the cell gap.
The thin film transistor array substrate includes gate lines and data lines, a thin film transistor formed as a switching device at each crossing area of the gate lines and the data lines, and a pixel electrode formed at each liquid crystal cell and connected to the thin film transistor. The gate lines and the data lines receive signals from gate circuits through pad parts, respectively. The thin film transistor applies a pixel voltage signal supplied to the data line to a pixel electrode in response to a scan signal supplied to the gate line.
The color filter array substrate includes a color filter formed at each liquid crystal cell, a black matrix partitioning off the color filters and blocking or reflecting external light, and a common electrode commonly applying a reference voltage to the liquid crystal cells.
The thin film transistor and the color filter array substrate are fabricated separately and bonded together, and then the liquid crystal is injected therebetween to complete the liquid crystal display panel.
The completed liquid crystal display panel goes through inspection processes such as a lighting-up test in order to detect the presence of defects. The liquid crystal display panel, as illustrated in FIG. 1 and FIG. 2, includes test pad parts 8, 18 and 20 for applying test signals for the inspection process.
A liquid crystal display panel 2 illustrated in FIG. 1 includes a picture display part 4 provided with a plurality of liquid crystal cells, a link pad part 6 formed at an outer area of the picture display part 4 and connected to a drive circuit (not shown), and a test pad part 8 used in the inspection process.
The link pad part 6 shown in FIG. 1 is connected to signal lines of the picture display part 4. The link pad part 6 applies the drive signal from an external drive circuit to the signal lines of the picture display part 4.
The test pad part 8 includes a plurality of test pads connected to the signal lines of the picture display part 4 and is formed separately from the link pad part 6. The test pad part 8 applies the test signals supplied in the inspection process of the liquid crystal display panel 2 and bias voltages supplied in an aging process to the signal lines of the picture display part 4.
The liquid crystal display panel 12 illustrated in FIG. 2 includes a picture display part 14 provided with a plurality of liquid crystal cells, a link pad part 16 formed at an outer area of the picture display part 14 and connected to a drive circuit (not shown), and test pad parts 18 and 20 used in the inspection process.
The test pad parts 18 and 20 illustrated in FIG. 2 includes a plurality of test pads connected to signal lines of the picture display part 14, and are formed to be integrated with the link pad part 16 on both sides of the link pad part 16. The test pad part 14 applies test signals supplied in the inspection process of the liquid crystal display panel 12 and bias voltages supplied in an aging process to the signal lines of the picture display part 14.
In fact, the test pad part, as illustrated in FIG. 3, includes a plurality of test pads 32 and a static electricity prevention circuit 36 connected to each of the test pads 32.
The test pads 32 illustrated in FIG. 3 are connected to the signal lines of the picture display part. Each static electricity prevention circuit 36 is connected between the test pad 32 and a first and second drive voltage supply line VSSL and VDDL. More specifically, the static electricity prevention circuit 36 consists of a first diode D1 connected between the first drive voltage supply line VSSL and the output terminal of the test pad 32, and a second diode D2 connected between the output terminal of the test pad 32 and the second drive voltage supply line VDDL. The static electricity prevention circuit 36, when static electricity flows through the test pads 32, is driven to cause the static electricity not to flow into the liquid crystal display panel and to bypass through the first and second drive voltage supply lines VDDL, VSSL, thereby protecting the picture display part in the liquid crystal display panel from the static electricity.
However, in the test pads with such a configuration, the test pads 32 are formed independently, thus an equipotential cannot be formed between the test pads 32. Due to this, in a fabricating process and an inspection process of the liquid crystal display panel, the static electricity flowing through the test pads 32 is not completely bypassed through the static electricity prevention circuit 36 and the first and second drive voltage supply lines VDDL and VSSL and transmitted into the liquid crystal display panel.
FIG. 4 illustrates another configuration of a test pad part.
The test pad part shown in FIG. 4 includes a plurality of test pads 42, a static electricity prevention circuit 46 connected to each test pad 42, and a shorting bar 44 commonly connected to the test pads 42.
The test pads 42 shown in FIG. 4 are connected to the signal lines of the picture display part and commonly connected to the shorting bar 44. The static electricity prevention circuit 46 is connected between the test pad 42 and the first and second drive voltage supply lines VSSL and VDDL. More specifically, the static electricity prevention circuit 46 includes a first diode D1 connected between the first drive voltage supply line VSSL and the output terminal of the test pad 42, and a second diode D2 connected between the output terminal of the test pad 42 and the second drive voltage supply line VDDL. The static electricity prevention circuit 46, when the static electricity flows through the test pads 42, is driven to cause the static electricity not to flow into the liquid crystal display panel and to bypass through the first and second drive voltage supply lines VDDL and VSSL. Accordingly, the static electricity prevention circuit 46 protects the picture display part in the liquid crystal display panel from the static electricity. Specifically, the test pads 42 have equipotential via the shorting bar 44. Accordingly, before the shorting bar 44 is removed in a scribing process, the static electricity flowing into the test pads 42 is diffused to the test pads 42 that form equipotential, thereby being bypassed more rapidly through the static electricity prevention circuit 36 and the first and second drive voltage supply lines VDDL and VSSL.
However, the test pad part illustrated in FIG. 4, after the shorting bar 44 is removed in the scribing process, has test pads 42 separated as shown in FIG. 3, thus the equipotential of the test pads 42 is no longer formed. Due to this, in the subsequent processes and the lighting-up test carried out after the scribing process, the static electricity flowing through the test pads 42 are not completely bypassed through the static electricity prevention circuit 46 and the first and second drive voltage supply lines VDDL and VSSL, but are transmitted into the liquid crystal display panel.
FIG. 5 illustrates still another configuration of the test pad part.
The test pad part illustrated in FIG. 5 includes a plurality of test pads 52, a plurality of static electricity prevention circuits 56 each connected to each inspection pad 52, respectively, a shorting bar 54 commonly connected to the test pads 52, and resistors R each connected between each test pad 52 and the shorting bar 54.
The test pads 52 illustrated in FIG. 5 are connected to signal lines of the picture display part and commonly connected to the shorting bar 54 through the resistors R. The static electricity prevention circuit 56 is connected between the test pad 52 and the first and second drive voltage supply lines VSSL and VDDL. More specifically, the static electricity prevention circuit 56 includes a first diode connected between the first drive voltage supply line VSSL and the output terminal of the test pad 52, and a second diode connected between the output terminal of the test pad 52 and the second drive voltage supply line VDDL. The static electricity prevention circuit 56, when the static electricity flows through the test pads 52, is driven to cause the static electricity not to flow into the liquid crystal display panel but to bypass through the first and second drive voltage supply lines VDDL, VSSL. Accordingly, the static electricity prevention circuit 56 protects the thin film transistor array inside the liquid crystal display panel from the static electricity. In addition, the static electricity flowing into the test pad 52 is made to bypass to the shorting bar 54 through the resistor R before the shorting bar 54 is removed in a grinding process.
However, because the connection is made through the resistor R, there is a limit for the static electricity flowing into the test pad 52 to be bypassed to the shorting bar 54, thereby allowing the static electricity to be transmitted into the liquid crystal display panel.
In this way, the test pad part of the related art does not effectively protect the thin film transistor inside the liquid crystal display panel from the static electricity flowing into the test pad in the fabricating process and the inspection process of the liquid crystal display panel even though the test pad is connected to the first and second drive voltage supply lines VDDL and VSSL.